Gun Counterparts
What the heck is a gun counterpart, you are asking?  Well, basically, it is the gun that the gun is based on.  Not the real life gun, but a gun from another game.  So here they are.  Now, some of the guns I didn't bother with, like shotgun, sniper rifle, rocket launcher, grenades, etc.  There is really no point to doing those.
Perfect Dark gun Goldeneye 007 gun
Joanna Dark's standard issue Falcon 2.  As futuristic as it looks, it is strangely similar to the DD44!  Large recoil, almost the exact same size, and same clip size.
No, your copy of Goldeneye 007 isn't missing a gun, that second picture is from Turok 2.  That gun is called the Mag60.  It fires a three round burst, just like the Magsec 4.  Turok 2 guns don't have clips, but the guns have very similar names, look a little like each other, and fire the same way.
I rely think that these two guns are based on each other.  The CMP150 has a very high firing rate, and the same clip size as the ZMG.  And if you say both names fast, they sort of sound similar.  I know that's a stretch, though.
The RC-P120 and the RC-P90.  I don't think that these two really need an explanation.  But, they look similar, fire fast, and have basically the same name, except for the numbers, obviously.
Now, a lot of people think that the K7 Avenger is like the KF7 Soviet, but think again.  These two guns, the Dragon and the KF7, have a lot in common.  Neither are exceptional guns, same clip size, medium damage and firing rate, and a medium zoom.
Again, no explanation is really required.  Basically the same name, powerful, fast firing, long zoom, high damage, both great guns.
The crossbow and the Tech Bow are somewhat similar...  Both are futuristic arrow launching devices.  The Tech Bow is from Turok 2, in case you didn't know.